Tag: respiration in humans

Not all cells use oxygen to produce energy. Aerobic cells use oxygen to produce energy. Anaerobic organisms do not require oxygen to produce energy. They obtain energy from metabolism in absence of oxygen. For example, yeasts in absence of oxygen convert sugar into alcohol and produces energy. This energy is then utilized for their survival.

The rate of respiration is highly dependent on concentration of carbon dioxide. The higher the concentration of carbon dioxide, less is the rate of respiration. Less the concentration of oxygen and more is the concentration of carbon dioxide, respiration rate increases.

• The combination of oxygen with haemoglobin is called oxyhaemoglobin and this oxygenated blood is carried away from the lungs through the bloodstream to all the tissues of the body. 
• Carbon monoxide can also bind to haemoglobin but does so about 240 times more tightly than oxygen, forming a compound called carboxyhaemoglobin. 
• This means that if both carbon monoxide and oxygen are inhaled, carbon monoxide will preferentially bind to haemoglobin. 
• This reduces the amount of haemoglobin available to bind to oxygen, so the body and tissues become starved of oxygen.

The characteristics of a respiratory surface are thin walls, a moist inner surface, a huge combined surface area, a rich blood supply each alveolus is sounded by capillaries. Surfaces which dries out easily, thick and easily damaged are not a characteristic of good respiratory surface. 

The respiratory rate or breathing frequency is the rate at which the number of inhalation and exhalation cycles are  taken within a set time.  The typical respiratory rate for a healthy adult at rest is 12–20 breaths per minute. However, the average resting respiratory rates differ with age. Food stimulates the nervous system which further tends to increase respiration rate.

The lack of oxygen or a lowering of the normal level of oxygen in the blood and body fluids is known as anoxemia and is generally experienced when in high altitudes.  

The majority of carbon dioxide molecules (85 percent) are carried as part of the bicarbonate buffer system. In this system, carbon dioxide diffuses into the red blood cells. Carbonic anhydrase (CA) within the red blood cells quickly converts the carbon dioxide into carbonic acid (H$ _2$CO$ _3$). Carbonic acid is an unstable, intermediate molecule that immediately dissociates into bicarbonate ions (HCO$ _3$−) and hydrogen (H+) ions. Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood, down its concentration gradient. It also results in the production of H+ ions. If too much H+ is produced, it can alter blood pH. However, hemoglobin binds to the free H+ ions, limiting shifts in pH. The newly-synthesized bicarbonate ion is transported out of the red blood cell into the liquid component of the blood in exchange for a chloride ion (Cl-). This is called the chloride shift. When the blood reaches the lungs, the bicarbonate ion is transported back into the red blood cell in exchange for the chloride ion. The H+ ion dissociates from the hemoglobin and binds to the bicarbonate ion. This produces the carbonic acid intermediate, which is converted back into carbon dioxide through the enzymatic action of CA. The carbon dioxide produced is expelled through the lungs during exhalation. 

Anaerobic respiration takes place in the absence of oxygen. So, oxidation of food does not take place. So, statement c is wrong. Gaseous exchange occurs through leaves that have minute tiny apertures over them called stomata. 

• When the internal intercostal muscles contract and diaphragm relax, the ribs move .downward and inward and the diaphragm becomes convex {dome shaped), 
• thus decreasing the volume of the thoracic cavity and increasing the pressure inside as compared to the atmospheric pressure outside. This will cause the air to move out (expiration).